JP5928983B2 - UV lamp for sterilization - Google Patents

Description

  The present invention relates to an ultraviolet lamp mainly used for sterilizing food packaging materials and containers using ultraviolet rays having a wavelength of 254 nm.

  The sterilization method using ultraviolet rays having a wavelength of 254 nm (sterilization line) has not been in danger of generating harmful substances, and has recently been particularly used as a highly safe sterilization means.

  However, an ultraviolet lamp using quartz as a material for the arc tube bulb emits ultraviolet light having a wavelength of 185 nm in addition to the germicidal line. Therefore, oxygen molecules in the air are dissociated to generate oxygen atoms. Atoms combine with oxygen molecules to produce ozone. Since ozone has a bactericidal action, it is useful depending on the conditions of use, but its toxicity becomes a problem when a person is near the ultraviolet treatment apparatus. Furthermore, when the ozone concentration is 0.1 ppm or more, it is harmful to the human body, so it is necessary to suppress the ozone concentration to 0.1 ppm or less.

  As a method for preventing ozone generation, conventionally, a lamp using ozone-less quartz is used for the arc tube bulb, or the arc tube adopts ordinary quartz, and the front glass of the UV irradiator incorporating the UV lamp is doped with titanium oxide. The method using the ozone-less quartz made is mentioned. For example, Japanese Patent Application Laid-Open No. H10-293826 is a document that describes this type of technology.

  However, when ozone-less quartz is adopted for the arc tube bulb, the transmittance absorption edge of the quartz shifts to the long wavelength side at a high temperature during lighting, so that in the wavelength region around the germicidal line, that is, in the wavelength range of 250 to 270 nm. There is a problem that the light transmittance decreases. Particularly in the case of a high-pressure discharge lamp, it is known that the outer surface of the arc tube becomes a high temperature of about 800 ° C. during operation. The broken line in FIG. 3 is a spectral transmittance curve at 800 ° C. of a conventional ozone-less quartz glass doped with titanium oxide.

  On the other hand, as a method for adjusting the light transmittance in the wavelength region of 200 to 300 nm, there is a method of forming a thin film coating on the surface of the arc tube bulb. For example, according to the method described in Patent Document 2, a thin film coating made of a composite oxide of a metal oxide such as tantalum (Ta) or niobium (Nb) and silicon (Si) oxide is formed by a dipping method or a vapor deposition method. The base material formed on the surface using a CVD method or the like can be used as a filter that can adjust the light transmittance in this wavelength region with a high degree of freedom.

  In the case of thin film coating, the wavelength shift characteristic of light transmittance with respect to temperature is opposite to that of quartz glass doped with a substance, and has a characteristic of shifting to the short wavelength side at high temperatures. For this reason, if the composition of the substance constituting the thin film coating is appropriately selected, there is a possibility that a high light transmittance can be secured in the wavelength region of 250 to 270 nm.

  However, the thin film coating certainly shows high thermal shock resistance and wear resistance when formed using a quartz glass flat plate as the base material, but the base material is not as simple as a lamp arc tube bulb. When it has a shape, there is a problem that the thermal shock resistance and the wear resistance are poor. In the curved portions at both ends of the arc tube bulb 11 and the periphery of the tip-off portion 21 that is a trace of arc tube sealing (see FIG. 1), cracking or peeling of the thin film coating occurs regardless of which coating method is used. easy. In addition, there is a disadvantage in that an extra step of thin film coating is added when manufacturing the lamp.

JP 2003-115281 A JP-A-9-184903

  The object of the present invention is to solve the above-mentioned problems, and to achieve both suppression of ozone generation and high UV intensity in the wavelength region of 250 to 270 nm, and high UV intensity is maintained even when used for a long time. It is to provide an ultraviolet lamp for sterilization.

  In order to solve the above problems, the present inventors consider that the surface of the arc tube bulb becomes a high temperature of about 800 ° C. during the operation of the high-pressure discharge lamp, and the transmittance absorption edge is maintained even at such a high temperature. It was recalled that doped quartz glass having characteristics that do not fall within the wavelength range of 250 to 270 nm with germicidal lines is used for the arc tube bulb of a high-pressure discharge lamp. As a doped material, attention was paid to a material other than titanium oxide that satisfies this characteristic condition.

Therefore, germicidal ultraviolet lamp of the present invention according to claim 1, therein a rare gas and mercury are enclosed, together with the comprised straight-tube luminous tube valve with the respective electrodes inside both ends, the light emitting bulb Is composed of silicon dioxide having oxygen-deficient defects, the defect content is 0.1 wt% or more and 1 wt% or less, and the transmittance absorption edge is a wavelength of 210 nm or more and 220 nm or less at room temperature, Is characterized by using a doped quartz glass having the property of shifting to the long wavelength side and having a characteristic of a wavelength of 230 nm or less at 800 ° C.

  Here, the “transmittance absorption edge” refers to a wavelength at which the light transmittance of the slope on the longest wavelength side of the absorption band in the ultraviolet region is 50% in the spectral transmittance curve.

  According to the first aspect of the present invention, the doped quartz glass of the arc tube bulb material has a transmittance absorption edge of 210 nm or more and 220 nm or less at room temperature, 230 nm or less at a high temperature of 800 ° C., and an ultraviolet ray having a wavelength of about 185 nm. Because the amount of ozone generated is suppressed within the specified range, and UV light with a wavelength of 254 nm necessary for sterilization has a significantly higher transmittance than conventional ones even at a high temperature of 800 ° C., the UV intensity is lit for 10,000 hours. An ultraviolet lamp for sterilization that can be secured later can be provided.

1 is a schematic external view of a sterilizing ultraviolet lamp according to an embodiment of the present invention. It is a figure which shows the spectral transmission factor in the normal temperature of an arc_tube | light_emitting_tube valve | bulb sample. It is a figure which shows the spectral transmission factor in 800 degreeC of an arc_tube | light_emitting_tube valve | bulb sample. It is a figure which shows the spectrum of the ultraviolet lamp using the arc tube bulb of each specification.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic external view for explaining an embodiment of the sterilizing ultraviolet lamp of the present invention. In FIG. 1, 11 is an arc tube bulb made of doped quartz glass having an outer diameter of 23.3 mm. At both ends of the bulb 11, electrodes 121 and 122 each having a structure in which the tip is wound in a coil shape are protruded inward of the bulb, and are arranged opposite to each other. The electrodes 121 and 122 use tungsten (W) as a material. At least one of these electrodes contains tungsten in an electron emitting substance.

The electrodes 121 and 122 are welded to one end of the metal foils 141 and 142, respectively. The other ends of the metal foils 141 and 142 are electrically connected to one ends of lead wires 151 and 152 made of, for example, molybdenum. The seal tube 13 is heated and melt-sealed from the welded portion of the electrodes 121 and 122 to one end of the lead wires 151 and 152. The metal foils 141 and 142 may be any material that has a thermal expansion coefficient close to that of the quartz glass that forms the seal tube 13, but molybdenum, for example, is used as a material that satisfies this condition. For example, 1.3 μg / mm ³ mercury and argon gas having a pressure of 2.7 kPa are enclosed in the bulb 11.

The other ends of the lead wires 151 and 152 are not illustrated via, for example, electric wires 171 and 172 having ultraviolet resistance electrically connected inside the ceramic bases 161 and 162, for example, coated with a fluorine resin. Connected to the power circuit.
Thus, the sterilizing ultraviolet lamp 100 which is a high-pressure mercury lamp is produced.

  Here, a comparative sterilizing ultraviolet lamp having the same specifications as the sterilizing ultraviolet lamp 100 except that the material of the arc tube bulb is conventional ozoneless quartz doped with titanium oxide is prepared separately, and the ultraviolet lamp A comparative evaluation experiment was conducted on the emission intensity of ultraviolet light near the germicidal line due to the difference in arc tube bulb material.

The specification (material) of the valve 11 is as follows. Specification 1 is a doped quartz glass according to an embodiment of the present invention, and specification 2 is a conventional ozoneless quartz glass in which quartz glass is doped with several percent of titanium oxide. The doped quartz glass of specification 1 produced a state in which oxygen atoms were deficient (so-called oxygen deficiency type defect) in a part of the Si—O network in silicon dioxide (SiO ₂ ), which is a component of pure quartz glass. Use materials. The defect content is preferably 0.1% by weight or more and 1% by weight or less. Quartz glass having an oxygen deficiency type defect is supposed to absorb ultraviolet rays having a wavelength of 200 to 250 nm due to generation of a so-called E prime center structure induced by ultraviolet rays in the vacuum ultraviolet region. By adjusting the defect content rate, the light transmittance in this wavelength region can be set to a desired value.

  The spectral transmittance curves of the valves of each specification in this experiment are shown in FIG. 2 for the room temperature around 20 ° C. and in FIG. 3 for the high temperature of 800 ° C. The spectral transmittance curve is obtained by measuring the light transmittance of each valve sample with a spectrophotometer. Here, the light transmittance of the bulb sample refers to the light transmittance measured by allowing light to enter the bulb surface perpendicularly to a semicylindrical sample piece obtained by cutting a cylindrical bulb along the tube axis. The light transmittance was measured in a state where foreign matters such as dust and dirt on the bulb surface were removed.

  First, looking at the spectral transmittance curve at room temperature shown in FIG. 2, the light transmittance of the specification 2 bulb is approximately 80 to 85% in the wavelength region of 250 to 260 nm, and 85% in the wavelength region of 260 nm or more. As described above, when the wavelength is 250 nm or less, the transmittance sharply decreases toward the short wavelength side, and the transmittance is 0% near the wavelength of 220 nm. The transmittance absorption edge is 233 nm.

  On the other hand, the bulb of the specification 1 is approximately 87 to 90% in the wavelength region of 250 to 260 nm, 90% or more in the wavelength region of 260 nm or more, and has a light transmittance higher than that of the conventional ozoneless quartz glass even at room temperature. In addition, the transmittance decreases as it goes to the short wavelength side at 250 nm or less, but the light transmittance is about 10 to several tens of percent higher than that of the conventional ozone-less quartz glass. The transmittance absorption edge is 215 nm.

  Next, looking at the spectral transmittance curve at a high temperature of 800 ° C. shown in FIG. 3, first, both specifications 1 and 2 are shifted to the longer wavelength side than at room temperature. Specification 2 is a wavelength region of 250 to 260 nm, and the light transmittance decreases from about 50% to about 20% toward the short wavelength side. Even in the wavelength region of 260 nm or more, the light transmission is not increased to 300 nm or more. The rate does not reach 90% or more. Even in the wavelength region of 250 nm or less, the light transmittance decreases toward 0% at 220 nm toward the short wavelength side. The transmittance absorption edge is 260 nm.

  On the other hand, the bulb of specification 1 has a high light transmittance of 77 to 83% in the wavelength region of 250 to 260 nm, 80% near the sterilization line (254 nm), and 88% or more at 300 nm or more. Further, even in the wavelength region of 250 nm or less, the decrease in light transmittance toward the short wavelength side is moderate as compared with the specification 2. The transmittance absorption edge is 225 nm.

Next, the evaluation result of the ultraviolet lamp produced using each bulb of the specifications 1 and 2 will be described.
FIG. 4 compares spectral spectra from the ultraviolet region to the visible region when an ultraviolet lamp using a bulb of each specification is lit at a lamp power of 1.6 kW in a dedicated lighting vessel. The emission intensity is shown as a relative value with the emission intensity at a wavelength of 365 nm of an ultraviolet lamp manufactured using a pure quartz glass bulb as 100.

  As can be seen from FIG. 4, the spectroscopic spectra of specifications 1 and 2 show a difference in the wavelength region of 300 nm or less, and particularly in the vicinity of the germicidal line, the emission intensity of the lamp of specification 1 is specified over a wide wavelength range of 20 to 30 nm. It was higher than 2 and about 20 times higher at the wavelength of 254 nm.

These differences in the spectrum are also reflected in the sterilization performance of the UV lamps according to both specifications. Using a UV sterilization test device equipped with UV lamps for specifications 1 and 2, respectively, the surface of the plastic container was irradiated with UV light, and a sterilization test was performed to measure the number of surviving indicator bacteria after irradiation. In order to obtain the sterilizing effect reduced to 10 ⁻⁶ before irradiation, the specification 2 lamp required about 20 minutes of UV irradiation, but for the specification 1 lamp, irradiation for 4 minutes was sufficient. It was. When comparing the ozone generation concentration, the ozone concentration in the case of the ultraviolet irradiation device equipped with the ultraviolet lamps of specifications 1 and 2 was measured. there were. Moreover, although the transition of the illumination intensity maintenance factor in wavelength 254nm was compared, the illumination intensity maintenance factor was 90% or more in the lighting time of 10000 hours of all the ultraviolet lamps of specification 1 and 2.

In the above description, an example in which doped quartz glass is a material in which oxygen-deficient defects are generated in quartz glass has been described. However, the present invention is not limited to this, and other materials may be used as doped quartz glass. In addition, a part of silicon dioxide, which is a component of pure quartz glass, is a substance whose transmittance absorption edge is a wavelength of 210 nm or more and 220 nm or less at room temperature and does not exist on the longer wavelength side than wavelength 230 nm even at a high temperature of 800 ° C. For example, it may be a material produced by replacing at least one selected from the group of metal oxides consisting of zirconium oxide (ZrO ₂ ), hafnium oxide (HfO ₂ ), niobium oxide (Nb ₂ O ₃ ), and the like. . The content of the metal oxide is preferably 0.1% by weight to 1% by weight. Or you may use the material which adjusted OH group content rate and fluorine content rate in quartz glass suitably.

  Titanium oxide has a strong absorption band in the near ultraviolet region, and it is difficult to adjust the transmittance by controlling the content rate, and it is preferable not to use it as a trace component to be contained in quartz glass.

  In short, in the present invention, doped quartz glass having a property that the transmittance absorption edge is 210 nm or more and 220 nm or less at room temperature, shifts to a long wavelength side at high temperature, and is 230 nm or less at 800 ° C. is used as a material. The same effect can be obtained with an ultraviolet lamp manufactured using a light-emitting tube bulb.

  The lower limit value of the preferable range of the transmittance absorption edge at a high temperature of 800 ° C. is not shown for the following reason. In other words, the width of the long wavelength shift at high temperature is about 10 nm in many cases, but the behavior of the transmittance absorption edge at high temperature is not independently defined, and is influenced by that at room temperature. This is because the width is slightly different from 5 to 15 nm depending on the kind and ratio of the substance contained in the material of the doped quartz glass, and the slope of the spectral transmittance curve is also slightly different.

If the transmittance absorption edge is less than 210 nm at room temperature, the light transmittance at 185 nm is not negligible, and ozone generation occurs, which is not preferable. Further, when the transmittance absorption edge is over 220 nm at room temperature, the transmittance absorption edge exceeds 230 nm at a high temperature of 800 ° C., and the transmittance near the sterilization line (254 nm) is about 70% or less. Therefore, the emission intensity of the germicidal line is not sufficient, which is not preferable.
In the present invention, the spectral transmittance characteristic of the doped quartz glass at a high temperature is specified at 800 ° C., for the following reason. That is, some ultraviolet lamps using the doped quartz glass as the arc tube material reach an arc tube surface temperature exceeding 800 ° C. when turned on, but the use limit on the high temperature side of the spectrophotometer used for measurement is 900 ° C. It is because it is a grade.

  As described above, according to the present invention, it is possible to provide an ultraviolet lamp capable of dramatically increasing the ultraviolet intensity at a wavelength of 254 nm while keeping the concentration of generated ozone within the specified range. Further, since the lamp can be manufactured from a material having a light transmittance adjusting function in the arc tube bulb itself, there is an advantage that it is not necessary to provide a separate coating process at the time of manufacturing the lamp as in the case of thin film coating.

  INDUSTRIAL APPLICABILITY The present invention can be used for an ultraviolet lamp used for sterilizing the surface of food packaging materials and containers.

DESCRIPTION OF SYMBOLS 100 ... Ultraviolet lamp 11 ... Light-emitting tube bulb 121, 122 ... Electrode 13 ... Sealing tube 141, 142 ... Metal foil 151, 152 ... Lead wire 161, 162 ... Base 171, 172 ... Electric wire 21 ... Chip-off part

Claims (1)

The arc tube bulb is composed of a straight tube type arc tube bulb in which rare gas and mercury are enclosed, and electrodes are respectively provided at both ends of the inside, and the arc tube bulb is composed of silicon dioxide having an oxygen deficiency type defect and contains the defect. The transmittance is 0.1% by weight or more and 1% by weight or less, the transmittance absorption edge has a wavelength of 210 nm or more and 220 nm or less at room temperature, and shifts to a long wavelength side at high temperature. A sterilizing ultraviolet lamp characterized by using doped quartz glass having the following characteristics.

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